Provide positional information when visiting ty, substs and closure_substs in MIR
This will enable the region renumbering portion of #43234 (non-lexical lifetimes). @nikomatsakis's current plan [here](https://gist.github.com/nikomatsakis/dfc27b28cd024eb25054b52bb11082f2) shows that we need spans of the original code to create new region variables, e.g. `self.infcx.next_region_var(infer::MiscVariable(span))`. The current visitor impls did not pass positional information (`Location` in some, `Span` and `SourceInfo` for others) for all types. I did not expand this to all visits, just the ones necessary for the above-mentioned plan.
e2b5d7e6b3